[Most of this material is quoted or paraphrased from two other sources as indicated following the material.]

“… Christians of the second century were already preparing for the feast of Easter with a two-day, grief-inspired fast,” (which would begin of course on Good Friday). “In the third century this fast (though not as a “complete fast”) was extended to all of Holy Week, as we learn from a letter of Dionysius of Alexandria. The first Ecumenical Council of Nicaea already speaks of the quadragesima paschae, i.e., the forty-day period of preparation for Easter, as something obvious and familiar to all.”

“The intention was to imitate Jesus who after his baptism in the Jordan fasted for forty days (Mt 4.2, Lk 4.1-2). The Church Fathers also saw in the practice an echo of the forty days Moses fasted on Sinai (Ex 34.28) and the forty days Elijah fasted on his journey to Mount Horeb (1Kings 19.8) as well as of the forty years of Israel’s sojourn in the wilderness; and so on.”

“The forty-day period originally began on the sixth Sunday before Easter and lasted until Holy Thursday when the solemn restoration of penitents to the community took place in Rome. There is disagreement about whether at one period in fourth-century Rome that fast was continued for only three weeks, as Socrates, the Greek historian of the Church, claims.”

“Because there was not fasting on Sundays, an effort was made in the fifth century to increase the number of actual fast-days to forty. The goal was attained in two stages. First, Good Friday and Holy Saturday were separated from the Easter Triduum and added to the preparatory fast, thus raising the number of fast-days to thirty-six… Soon, however, the four weekdays before the first Sunday of Lent were added, changing the number once again to forty. Thus we have our Ash Wednesday as the beginning of Lent.”
(From The Liturgical Year its history & its meaning after the reform of the liturgy by Adolf Adam, p 91f)

“It had been decided at a very early time that the special penance for those guilty of a serious sin (a “capital sin”) should start at the beginning of Lent; that is, originally on the Monday after the first Sunday, but later on Ash Wednesday. Penitents donned a penitential garment and had ashes sprinkled on them. Then came the rite of expulsion from the Church,… The wearing of a special penitential garment and the sprinkling with ashes as an expression of sorrow and repentance were already familiar to the Old Testament and pagan antiquity.”

“Although the institution of public ecclesiastical penance disappeared toward the end of the first millennium, this rite of ashes was retained and applied now to all the faithful. At the Synod of Benevento (1091) Pope Urban II recommended this custom to all the churches. Clerics and laymen had the ashes sprinkled on their heads, while women had a sign of the cross made with ashes on their foreheads. A special prayer for the blessing of the ashes appears first in the eleventh century. The rule that the ashes were to be obtained by burning the palm branches from the previous year occurs for the first time in the twelfth century. From antiquity and the Old Testament down to the most recent Church documents the action is always seen as a symbol of transiency, sorrow and penance.”
(From The Liturgical Year its history & its meaning after the reform of the liturgy by Adolf Adam, p 97f)

Ash Wednesday unlike other “fest” days celebrated during the church year commemorates neither an “idea” nor an “event.” Rather it is simply the first day of Lent. “But what seems to give Ash Wednesday its peculiar character and content is not its history, or its lessons, but a practice – the imposition of ashes.” It is a day of recognition of mortality, repentance, and purification. All three of these, of course, are themes of Lent, but they appear with particular force at the opening of the season.

There is not doubt these three images are connected with ashes. The first is the clearest – ashes are the dead remains of something which was once alive. But in case we miss the connection, the saying for imposition reminds us: “Remember you are dust, and to dust you shall return.”

For the second case, there are stories throughout the Bible where ashes are a sign of repentance and mourning. “Ashes are a sign of Tamar’s grief after her rape by Amnon (2 Samuel 13:19); of the grief of Mordecai and the Jews upon learning of the impending holocaust (Esther 4:1,3); and of Job’s affliction (Job 2:80). But they are also a sign of repentance of Job (Job 42:6); as well as that of Daniel on behalf of exiled Israel (Daniel 9:3); of the king of Nineveh upon hearing Jonah’s message of doom (Jonah 3:6); and in the New Testament of Sodom and Gomorrah (Matthew 11:21 and Luke 10:13). To those steeped in the biblical stories, ashes call to mind both grief and repentance.”

“The connection between ashes and cleansing is less obvious to us than it would be to those who made lye from wood ashes. But even in our own day Heloise (of “Hints from”) reminds us that a paste made with fireplace ashes is the best way of cleaning a glass fireplace door. The grit and chemical composition of ashes make them useful in purification.”
(From the draft for a book, Here and Now: the Year in the Presence of the Resurrected Christ, by the Reverend Doctor Mark Oldenburg, Lutheran Theological Seminary at Gettysburg)